Justification:
This species is listed as Least Concern given its relatively large range in Bolivia, and because hunting pressure on this species is not thought to have resulted in a decline that would warrant listing the species in a threatened category.

Alouatta sara is believed to occur only in Bolivia. Anderson (1997) gives a range extending from the Department of Pando south along the Andean Cordillera and east into central Bolivia including the entire basin of the Río Beni and east as far the Mamoré-Guapore. Its sympatry with Alouatta caraya over a large part of its range east of the Río Beni is poorly understood, but the indications are that there may be some subtle, but distinct difference in habitat preferences, with A. sara prevailing in humid forest areas and seasonally flooded forest along major rivers (for example, igapó along the Río Iteñez) and A. caraya being found in drier, semdeciduous forest and gallery forest in areas of savanna and chaco (see for example, Wallace et al. 1998)

This species is found up to 1,000 m in tropical forest including riverine forest and seasonally flooded forests. During their primate surveys in the Noel Kempf Mercado National Park, Bolivia, Wallace et al. (1998) found Alouatta sara only (n=20) in igapó forest (seasonally inundated forest) along the Río Iteñez.

The howler monkeys are the large leaf-eaters of the South American primate communities. The molar teeth are particularly adapted for their chewing leaves through shearing. They spend up to 70% of their day lying and sitting about quietly among the branches, fermenting leaves in their enlarged caecums. Like the spider monkeys, they are prehensile-tailed, with a naked patch of skin on the under surface at the tip. Their most characteristic feature is the deep jaws which surround the enlarged larynx and hyoid apparatus, a resonating chamber. It is with this enlarged and highly specialized voice box that they produce their howls (grunts, roars and barks). Howling sessions, usually involving the entire group, can be heard particularly in the early morning and are audible at distances of 1-2 kms (Drubbel and Gautier 1993). The red howlers (A. seniculus, A. macconnelli, A. juara, A. puruensis, and A. sara) have the largest voice boxes and the deepest roars, while the Mexican, Central American and northern Colombian mantled howlers, A. palliata and A. pigra, have the smallest, and their howls are more high pitched as a result.

Red howler groups are usually small, ranging in size from 2-16 animals and averaging 4-10 (Neville et al. 1988). Wallace et al. (1998) recorded an average group size of 3.3±2.0 individuals (range 1-7, n=18) in the Noel Kempff Mercado Nation Park in eastern central Bolivia. In the red howlers, there is usually only one dominant male in the group (occasionally two), others being sub-adults, or juveniles, along with a harem of two to five females. Unlike the spider monkeys, and related to the large proportion of leaves in the diet (up to 50% of the annual diet), the howler monkeys generally have quite small and broadly overlapping home ranges, of 5 ha up to 45 ha, depending on the type of habitat (Neville et al. 1988).

Howlers are the only New World primates which regularly include mature leaves in their diet, although softer, less fibrous, young leaves are preferred when they are available. Their folivory and ability to eat mature leaves is undoubtedly one of the keys to their wide distribution and the wide variety of vegetation types they inhabit. Mature fruit is the other important food item, especially wild figs (Ficus) in many regions, but they also eat leaf petioles, buds, flowers (sometimes seasonally very important), seeds, moss, stems and twigs, and termitaria.

Oestrus lasts 2-4 days, with intervals between oestrous periods of about 17 days. Interbirth intervals are generally about 16.6 months, although they may be shortened by the death of an infant to about 10.5 months (Crockett and Sekulic 1984). Mean gestation length is 191 days (range 186-194, n=6) (as for A. seniculus seniculus in Crockett and Sekulic 1982).